A type of audio mixer combining two audio signals, and outputting their sum and difference. The frequencies found in the original signals are not passed through to the output. For example, if two sine waves (single frequency waveforms containing no overtones) are inputted, one with a frequency of 1000 Hz, and the second at 400 Hz, the ring modulator will output two frequencies: 600 Hz and 1400 Hz. With more complex waveforms (which contain many more overtone frequencies) ring modulators produce a clangorous, “metallic” result often used for special effects, in synth programming, and so on. One popular use has been to process vocals, which produces sci-fi sounding “robotic” voices.